Nuclear Factor-kappa B (NF-kB) is a transcription factor that not only contributes to the aging process itself, but is believed to play an integral role in the development and pathogenicity of many diseases associated with aging, including cancer. In particular, NF-kB is implicated in multiple myeloma (MM), a hematologic malignancy that is exceptionally common in older patients and is characterized by the clonal expansion of plasma B cells in the bone marrow. 80% of patients with this disease are over 60 years old. Despite recent advances in chemo and transplant therapy, MM has a median survival of only three years. Thus, advancement of therapy will require a better understanding of the biology of this disease. Primary myeloma cells possess active NF-kB, which appears to be crucial for tumor survival. NF-kB also plays a role in the interactions between tumor cells and their supporting microenvironment, including bone marrow stromal cells (BMSCs). The proteasome inhibitor bortezomib is believed to work at least in part through the inhibition of NF-kB activity, and was recently approved for the treatment of MM. While this drug has had relative success in the clinic, initial and developed resistance to bortezomib are common occurrences. The exact molecular mechanisms of bortezomib and those that mediate resistance to the drug are not completely understood. Our preliminary studies suggest that constitutive NF-kB in the majority of both primary patient and MM cell lines is resistant to bortezomib treatment. We also observe that co- culture of MM cells with BMSCs derived from MM patients, and not those derived from non-MM patients, further activates NF-kB in these cells, and that this enhanced activity is also mostly resistant to bortezomib treatment. Through mutational and biochemical analysis, this proposal addresses the molecular mechanisms of bortezomib resistant NF-kB activity in MM cells. The specific goals of this proposal are to delineate the cis-elements of IkBa that are required for it to be a substrate of bortezomib-resistant degradation, and to identify novel upstream activators of bortezomib-resistant NF-kB in MM. These studies will help to better understand the virulence of the age-associated malignancy, MM, and to improve the health and well-being of older patients affected by this disease. Relevance: NF-kB is a protein that can help tumor cells survive and defend themselves against chemotherapy. By understanding the regulation of NF-kB, we may be able to better predict if a patient will respond to chemotherapies, and to discover new drugs. This will help avoid subjecting patients to the side effects of these drugs unnecessarily.